AN EXPERIMENTAL STUDY OF ANGULAR VARIATIONS OF …...An experimental study of angular variations of brightness surface temperature for some natural surfaces. Cuenca et al.- AATSR Workshop

An experimental study of angular variations of brightness surfacAn experimental study of angular variations of brightness surface temperature for some natural surfaces.e temperature for some natural surfaces.Cuenca et al.Cuenca et al.-- AATSR Workshop. Rome, 29th September 2005.AATSR Workshop. Rome, 29th September 2005. 11

AN EXPERIMENTAL STUDY OF ANGULAR AN EXPERIMENTAL STUDY OF ANGULAR VARIATIONS OF BRIGHTNESS SURFACE VARIATIONS OF BRIGHTNESS SURFACE

TEMPERATURE FOR SOME NATURAL TEMPERATURE FOR SOME NATURAL SURFACESSURFACES

J. Cuenca, J. A. Sobrino, G. SòriaJ. Cuenca, J. A. Sobrino, G. Sòria

Global Change UnitGlobal Change UnitDpt. of Thermodynamics Dpt. of Thermodynamics -- University of ValenciaUniversity of Valencia

c.c.// Dr. Moliner, 50Dr. Moliner, 5046100 Burjassot (Valencia)46100 Burjassot (Valencia)

[email protected], [email protected]@uv.es, [email protected], [email protected], [email protected]


PRESENTATION SCHEMEPRESENTATION SCHEME

1.1.-- THEORYTHEORY

2.2.-- EXPERIENCESEXPERIENCES

3.3.-- RESULTSRESULTS

4.4.-- CONCLUSIONSCONCLUSIONS


1.1.-- THEORYTHEORY

Starting from LSBT (Land Surface Brightness Temperature functionStarting from LSBT (Land Surface Brightness Temperature function):):

)](I[B)(LSBT sur1 θ=θ λ−λ

θθ: zenith observation angle: zenith observation angle

IIλλsurfacesurface((θθ): radiance measured by the sensor coming from the surface ): radiance measured by the sensor coming from the surface

en the wavelength en the wavelength λλBBλλ

--11 : inverse of Planck: inverse of Planck’’s functions function

∑=

θ−θ=θ∆n

1iiii )(LSBT

n1)(LSBT)(LSBT

McAteeMcAtee et al.et al. (2003)(2003)

∆∆LSBT is used because it minimizes the effect of temporal changesLSBT is used because it minimizes the effect of temporal changesin temperature during an angular scan cyclein temperature during an angular scan cycle..


11..-- THEORYTHEORYOperative expressions: Operative expressions: EmissivityEmissivity estimationestimation

)/T(- exp 1,3 - )/T(- exp)/T(- exp 1,3 - )/T(- exp

=iatm0,iSi

iatm0,iirad,ii αα

ααε θDirectional absolute Directional absolute emissivityemissivity

)/T(- exp 1,3 - )/T(- exp)/T(- exp 1,3 - )/T(- exp

=iatm0,iirad0,i

iatm0,iirad,iir, αα

ααε θDirectional relative Directional relative emissivityemissivity

(Sobrino & Cuenca, 1999; Cuenca & Sobrino, 2004)(Sobrino & Cuenca, 1999; Cuenca & Sobrino, 2004)

They are obtained from 3 measurements: They are obtained from 3 measurements: TTrad,irad,i, T, Tatm0,iatm0,i and Tand Tss or Tor Trad,0rad,0

method error:method error: δεδεiiθθ == δεδεr, ir, iθθ = 0,005= 0,005


22..-- EXPERIEXPERIENCES: MaterialENCES: Material

1.1.-- Own developmentOwn development

GoniometersGoniometers

2.2.--InstrumentationInstrumentation

Radiometer Omega OS86Radiometer Omega OS86

Radiometer Radiometer RaytekRaytek ThermalertThermalert MIDMID

Radiometer Everest 3000.4ZLCRadiometer Everest 3000.4ZLC

Radiometers Radiometers CimelCimel 312312--1 & 21 & 2

Thermal Camera Thermal Camera IrisysIrisys IRI 1001IRI 1001

Calibration sourcesCalibration sources


2.2.-- EXPERIENCES: EXPERIENCES: GoniometersGoniometers

arc arc goniometergoniometer

arm arm goniometergoniometer

automatic automatic goniometergoniometer


2.2.-- EXPERIENCES: InstrumentsEXPERIENCES: Instruments

Raytek Thermalert MIDRaytek Thermalert MIDOmega OS86Omega OS86

PASS BANDPASS BAND: 8: 8--14 14 µµmm

RESOLUTIONRESOLUTION: 0.1 K: 0.1 K

PRECISSIONPRECISSION: : ±± 0.5 K0.5 K

IFOVIFOV: 2: 2ºº--2020ºº

Everest 3000.4ZLCEverest 3000.4ZLC


22..-- EXPERIMENEXPERIMENCES: CES: InstrumentsInstrumentsSPECTRAL BANDSSPECTRAL BANDS

CimelCimel 312312--11 CimelCimel 312312--22Channel 1: 8Channel 1: 8--13 13 µµmm Channel 1: 8Channel 1: 8--13 13 µµmmChannel 2: 11.5Channel 2: 11.5--12.5 12.5 µµmm Channel 2: 11.0Channel 2: 11.0--11.7 11.7 µµmmChannel 3: 10.5Channel 3: 10.5--11.5 11.5 µµmm Channel 3: 10.3Channel 3: 10.3--11.0 11.0 µµmmChannel 4: 8.2Channel 4: 8.2--9.2 9.2 µµmm Channel 4: 8.9Channel 4: 8.9--9,3 9,3 µµmm

Channel 5: 8.5Channel 5: 8.5--8.9 8.9 µµmmChannel 6: 8.1Channel 6: 8.1--8.5 8.5 µµmm

RESOLUTIONRESOLUTION: 8 : 8 mKmK in the broad bandin the broad band50 50 mKmK in the others (at 20in the others (at 20ººC)C)

PRECISSIONPRECISSION: : ±± 0.5 K0.5 K

IFOVIFOV: 10: 10ºº

RadiometerRadiometer Cimel 312Cimel 312

PASS PASS BANDBAND: : 88--14 14 µµmm

RESOLURESOLUTIOTIONN: : 00..1 K1 K

PRECISPRECISSIOSIONN: : ±± 00..5 K5 K

IFOVIFOV: : 2200ººx 20x 20º

Thermal camera Thermal camera IrisysIrisys IRI 1001IRI 1001

º


22..-- EXPERIMENEXPERIMENCES:CES:Calibration sources

Galai 204Galai 204--PP

Everest 1000Everest 1000


22..-- EXPERIENCEXPERIENCESES: : FIELD CAMPAIGNSFIELD CAMPAIGNS

BarraxBarrax zone Landsatzone Landsat--7 image, with EAGLE 7 image, with EAGLE study area.study area.

Aerial photography of Aerial photography of BarraxBarrax study area.study area.


2.2.-- EXPERIENCES: SAMPLESEXPERIENCES: SAMPLESHOMOGENEOUS SAMPLESHOMOGENEOUS SAMPLES

clayclay sandsand

slimeslimegravelgravel

grassgrass


2.2.-- EXPERIENCES: SAMPLESEXPERIENCES: SAMPLESWATERMEDWATERMED--SPARC 2003SPARC 2003

wheatwheat

alfalfaalfalfa bare soilbare soil

grass (2)grass (2)

sugar beetsugar beet


2.2.-- EXPERIENCES: SAMPLESEXPERIENCES: SAMPLESEAGLEEAGLE--SPARC 2004 and 2005SPARC 2004 and 2005

bare soilbare soil

grassgrass


3.3.-- RESULTSRESULTSHOMOGENEOUS SAMPLESHOMOGENEOUS SAMPLES (8(8--14 14 µµm)m)

0.86

0.88

0.9

0.92

0.94

0.96

0.98

0 10 20 30 40 50 60 70

angle (º)

abso

lute

ε w ater

sand

clay

slime

gravel

0.94

0.95

0.96

0.97

0.98

0.99

1

1.01

0 10 20 30 40 50 60 70

angle (º)

rela

tive

ε w ater

sand

clay

slime

gravel

Decrease in relative

emissivity (%)

Decrease in absolute

emissivity(%)sample

water 3,3 3,3

sand 2,0 1,9

clay 0,5 0,5

slime 0,9 0,9

gravel 1,2 1,2

grass 0 0

Angular variation of Angular variation of emissivityemissivitybetween 0between 0ºº and 55and 55ºº

((SobrinoSobrino & Cuenca, 1999)& Cuenca, 1999)


3.3.-- RESULTSRESULTSHOMOGENEOUS SAMPLESHOMOGENEOUS SAMPLES (8(8--14 14 µµm)m)

0.880.89

0.90.910.920.93

0.940.950.960.97

0.980.99

0 10 20 30 40 50 60 70

angle (º)

abso

lute

ε

this workRees&James

Results comparison: Rees & James (1992) Results comparison: Rees & James (1992) and ours for water.and ours for water.

Results comparison: Results comparison: LabedLabed & Stoll (1991) & Stoll (1991) and ours for sand. 0.96

0.97

0.98

0.99

1

1.01

0 20 40 60 80

angle (º)

rela

tive

εthis workLabed&Stoll

and ours for sand.


3.3.-- RESULTSRESULTSHOMOGENOUS SAMPLES (4 CHANNELS)HOMOGENOUS SAMPLES (4 CHANNELS)

channel 1 (8-13 µm)

0.940

0.960

0.980

1.000

0 20 40 60

angle (º)

rela

tive

ε

watersandclayslimegravel

channel 2 (11.5-12.5 µm)

0.940

0.960

0.980

1.000

0 20 40 60

angle (º)

rela

tive

ε

water

sandclay

slime

gravel

channel 3 (10.3-11-3 µm)

0.940

0.960

0.980

1.000

0 20 40 60

angle (º)

rela

tive

ε

watersandclayslimegravel

channel 4 (8.2-9.2 µm)

0.940

0.960

0.980

1.000

0 20 40 60

angle (º)

rela

tive

ε

watersand

clayslime

gravel

(Cuenca & Sobrino, 2004)(Cuenca & Sobrino, 2004)


3.3.-- RESULTSRESULTSHOMOGENEOUS SAMPLES (4 CHANNELS) HOMOGENEOUS SAMPLES (4 CHANNELS) –– RESULTS COMPARISONRESULTS COMPARISON

water: channel 1 (8-13 µm)

0.950

0.960

0.970

0.980

0.990

1.000

1.010

0 20 40 60

angle (º)

rela

tive

ε

Masuda et al.this work

water: channel 2 (11.5-12.5 µm )

0.950

0.960

0.970

0.980

0.990

1.000

1.010

0 20 40 60

angle (º)

rela

tive

ε


water: channel 3 (10.3-11-3 µm)

0.950

0.960

0.970

0.980

0.990

1.000

1.010

0 20 40 60

angle (º)

rela

tive

ε


water: channel 4 (8.2-9.2 µm)

0.950

0.960

0.970

0.980

0.990

1.000

1.010

0 20 40 60

angle (º)

rela

tive

εMasuda et al.this work


3.3.-- RESULTSRESULTSHEATED SAMPLES (6 CHANNELS + THERMAL CAMERA)HEATED SAMPLES (6 CHANNELS + THERMAL CAMERA)

0.860.880.9

0.920.94

0.960.98

11.02

0 20 40 60

angle (º)

rela

tive

ε

ε1 (8-13µm)ε2 (11,0-11,7µm)ε3 (10,3-11,0µm)ε4 (8,9-9,3µm)ε5 (8,5-8,9µm)ε6 (8,1-8,5µm)εCM (8-14µm)

0.930.940.950.96

0.970.980.99

11.01

0 20 40 60

ángulo (º)

rela

tive

ε

ε1 (8-13µm)ε2 (11,0-11,7µm)ε3 (10,3-11,0µm)ε4 (8,9-9,3µm)ε5 (8,5-8,9µm)ε6 (8,1-8,5µm)εCM (8-14µm)

sandsand

slimeslime

Results:Results: emissivityemissivity decrease between 0

decrease between 0ºº and 55and 55ºº::

Broad band:Broad band:

sand and slime: 5%sand and slime: 5%

Channels lower Channels lower λλ::

higher dependence: up to higher dependence: up to 12% (sand)12% (sand)


3.3.-- RESULTSRESULTSWATERMEDWATERMED--SPARC 2003SPARC 2003 IN SITUIN SITU MEASUREMENTSMEASUREMENTS

Double study:Double study:

1.) depending on 1.) depending on λλ: : CimelCimel 312312--1 (4 channels)1 (4 channels)

2.) depending on 2.) depending on IFOVIFOV: (all 8: (all 8--14 14 µµm)m)

Everest 3000 (4Everest 3000 (4ºº))

broad band of broad band of CimelCimel 312312--1 (101 (10ºº))

RaytekRaytek MID (20MID (20ºº))


3.3.-- RESULTSRESULTSWATERMEDWATERMED--SPARC 2003 SPARC 2003 IN SITUIN SITU MEASUREMENTSMEASUREMENTS

-3

-2

-1

0

1

2

3

-60 -40 -20 0 20 40 60

angle (º)

∆LS

BT

(K) C1 (8-13µm)

C2 (11,5-12,5µm)

C3 (10,3-11,3µm)

C4 (8,2-9,2µm)

-3

-2

-1

0

1

2

3

-60 -40 -20 0 20 40 60

angle (º)

∆LS

BT

(K)

EVEREST

CIMEL

RAYTEK

alfalfaalfalfa

∆∆LSBT reaches an amplitude of LSBT reaches an amplitude of ±±1.5 1.5 K (K (CimelCimel channels) but increases channels) but increases significantly at the second graphic.significantly at the second graphic.⇒⇒ Great thermal heterogeneity of Great thermal heterogeneity of the sample.the sample.Up from 30Up from 30ºº is observed great is observed great dependence with IFOV. dependence with IFOV. In these conditions is not feasible to In these conditions is not feasible to study study ∆ε∆εθθ ..


3.3.-- RESULTSRESULTSWATERMEDWATERMED--SPARC 2003 SPARC 2003 IN SITUIN SITU MEASUREMENTSMEASUREMENTS

If narrow IFOVIf narrow IFOV⇒⇒ problem: thermal heterogeneity: measurements strongly problem: thermal heterogeneity: measurements strongly dependent of pointing place dependent of pointing place ⇒⇒ results not representative of the surface.results not representative of the surface.If considerably wider IFOV If considerably wider IFOV ⇒⇒ problem: it gets lost the concept of directionality problem: it gets lost the concept of directionality of the measure.of the measure.Possibility to solve both problems: radiometer with narrow IFOV Possibility to solve both problems: radiometer with narrow IFOV placed at a placed at a ““largelarge”” distance of the sample.distance of the sample.

ConclusionConclusion:: it is needed to study the samples (the thermal distribution) anit is needed to study the samples (the thermal distribution) and the d the measuring conditions in each experience for to define the most ameasuring conditions in each experience for to define the most appropriate ppropriate methodology of the experimental procedure.methodology of the experimental procedure.

Sample │∆LSBTmax(λ)│(K) │∆LSBTmax(IFOV)│(K)Bare soil 1.5 1

Grass 5 1

Alfalfa 1.5 2.5

Sugar beet 2.5 2

Wheat 3 1.5

∆∆LSBT maximal LSBT maximal amplitudes depending amplitudes depending on the thermal channels on the thermal channels and IFOV of the used and IFOV of the used instrumentinstrument


3.3.-- RESULTSRESULTSEAGLEEAGLE--SPARC 2004 SPARC 2004 IN SITUIN SITU DAY AND NIGHT MEASUREMENTSDAY AND NIGHT MEASUREMENTS

Measurements:Measurements: with with CimelCimel 312312--1 radiometer (4 canales)1 radiometer (4 canales)

with with CimelCimel 312312--2 radiometer (6 canales)2 radiometer (6 canales)

with thermal camerawith thermal camera

3 graphics : 3 graphics : CimelCimel 312312--1 (4 channels), 1 (4 channels), CimelCimel 312312--2 (6 channels) and broad bands of both 2 (6 channels) and broad bands of both CimelCimel and thermal camera. Besides: Radiometric temperature maps with and thermal camera. Besides: Radiometric temperature maps with thermal camera.thermal camera.

Day and night measurements on the grass. EAGLEDay and night measurements on the grass. EAGLE--SPARC 2004SPARC 2004



-3

-2

-1

0

1

2

3

-60 -40 -20 0 20 40 60

angle (º)

∆LS

BT (K

) C1 (8-13µm)C2 (11,5-12,5µm)C3 (10,3-11,3µm)C4 (8,2-9,2µm)

-3

-2

-1

0

1

2

3

-60 -40 -20 0 20 40 60

angle (º)

∆LS

BT

(K)

C1 (8-13µm )

C2 (11,0-11,7µm )C3 (10,3-11,0µm )

C4 (8,9-9,3µm )C5 (8,5-8,9µm )

C6 (8,1-8,5µm )

-3

-2

-1

0

1

2

3

-60 -40 -20 0 20 40 60

angle (º)

∆LS

BT

(K) C1 (8-13µm )

C2 (11,5-12,5µm )

C3 (10,3-11,3µm )

C4 (8,2-9,2µm )

-3

-2

-1

0

1

2

3

-60 -40 -20 0 20 40 60

angle (º)

∆LS

BT

(K)

C1 (8-13µm )C2 (11,0-11,7µm )

C3 (10,3-11,0µm )C4 (8,9-9,3µm )

C5 (8,5-8,9µm )C6 (8,1-8,5µm )

-3

-2

-1

0

1

2

3

-60 -40 -20 0 20 40 60

angle (º)

∆LST

B (K

)

thermal cam.Cimel 4Cimel 6

-3

-2

-1

0

1

2

3

-60 -40 -20 0 20 40 60

angle (º)

∆LST

B (K

)


dayday nightnight

bare soilbare soil



dayday nightnight

bare soilbare soil

-50º 50º

0º

40-4238-4036-3834-3632-3430-32

-30º 30º

-50º 50º

0º

18-1917-1816-1715-1614-1513-14

-30º 30º



-3

-2

-1

0

1

2

3

-60 -40 -20 0 20 40 60

angle (º)

∆LS

BT

(K) C1 (8-13µm )

C2 (11,5-12,5µm )

C3 (10,3-11,3µm )C4 (8,2-9,2µm )

-3

-2

-1

0

1

2

3

-60 -40 -20 0 20 40 60

angle (º)

∆LS

BT

(K)

C1 (8-13µm )C2 (11,0-11,7µm )

C3 (10,3-11,0µm )C4 (8,9-9,3µm )

C5 (8,5-8,9µm )C6 (8,1-8,5µm )

-3

-2

-1

0

1

2

3

-60 -40 -20 0 20 40 60

angle (º)

∆LS

BT

(K) C1 (8-13µm )

C2 (11,5-12,5µm )

C3 (10,3-11,3µm )C4 (8,2-9,2µm )

-3

-2

-1

0

1

2

3

-60 -40 -20 0 20 40 60

angle (º)

∆LS

BT

(K)

C1 (8-13µm )C2 (11,0-11,7µm )

C3 (10,3-11,0µm )C4 (8,9-9,3µm )

C5 (8,5-8,9µm )C6 (8,1-8,5µm )

-3

-2

-1

0

1

2

3

-60 -40 -20 0 20 40 60

angle (º)

∆LST

B (K

)


-3

-2

-1

0

1

2

3

-60 -40 -20 0 20 40 60

angle (º)

∆LST

B (K

)


dayday nightnight

grassgrass



nightnight

grassgrass

-50º 50º

0º

33-3432-3331-3230-3129-3028-29

-30º 30º

-50º 50º

0º

17-1816-1715-1614-1513-1412-13

- 30 º 30º

dayday


3.3.-- RESULTSRESULTSEAGLEEAGLE--SPARC 2004 SPARC 2004 IN SITUIN SITU NIGHT MEASUREMENTSNIGHT MEASUREMENTS

0.9

0.92

0.94

0.96

0.98

1

1.02

-60 -40 -20 0 20 40 60

angle (º)

rela

tive

ε C1 (8-13µm)C2 (11,5-12,5µm)C3 (10,3-11,3µm)C4 (8,2-9,2µm)

0.9

0.92

0.94

0.96

0.98

1

1.02

-60 -40 -20 0 20 40 60

angle (º)

rela

tive

ε

C1 (8-13µm)C2 (11,0-11,7µm)C3 (10,3-11,0µm)C4 (8,9-9,3µm)C5 (8,5-8,9µm)C6 (8,1-8,5µm)

bare soilbare soil

0.9

0.92

0.94

0.96

0.98

1

1.02

-60 -40 -20 0 20 40 60

angle (º)

ε rel

ativ

e ε C1 (8-13µm)

C2 (11,5-12,5µm)C3 (10,3-11,3µm)C4 (8,2-9,2µm)

0.9

0.92

0.94

0.96

0.98

1

1.02

-60 -40 -20 0 20 40 60

angle (º)

rela

tive

ε

C1 (8-13µm)C2 (11,0-11,7µm)C3 (10,3-11,0µm)C4 (8,9-9,3µm)C5 (8,5-8,9µm)C6 (8,1-8,5µm)

0.9

0.92

0.94

0.96

0.98

1

1.02

-60 -40 -20 0 20 40 60

ángulo (º)

ε rel

ativ

a thermal cam.

Cimel 4Cimel 6

0.9

0.92

0.94

0.96

0.98

1

1.02

-60 -40 -20 0 20 40 60

angle (º)

rela

tive

ε thermal cam.

Cimel 4

Cimel 6

εε εε

grassgrass


4.4.-- CONCLUSIONSCONCLUSIONS

1 .- We have evaluated the ∆εθ in homogeneous samples between 0º and 65º in the 8-14 µm band. The results show a general decrease of the ε with the observation angle. Water shows the biggest decrease in ε (about 7%).

2.- We have evaluated the ∆εθ of the same samples in 4 spectral bands. The results show an angular dependence of ε with the observation angle and λ.

3.- It has been studied the angular variation of radiometric temperature from in situmeasurements on natural surfaces. From the study it is concluded that the results depend strongly on the sensor’s IFOV, being greater the heterogeneity with narrower IFOV.

4.- It has been found for function ∆LSBT a thermal variation of up to ±2.5 K for some samples, which indicates that the measurement on these surfaces doesn’t allow to evaluate ∆εθ because it are done not comparable observations at several angles.

5.- We have calculated the ∆εθ on a natural sample of bare soil and grass in night conditions. The results show a nearly inexistent dependence of the emissivity with the observation angle at the studied soil, and the influence of humidity at grass.

6.- We have showed the power of an image sensor (thermal camera) for having a precise control on the observed spot by the radiometer, with the aim of assuring the thermal homogeneity of the sample.

Documents

AN EXPERIMENTAL STUDY OF ANGULAR VARIATIONS OF …...An experimental study of angular variations of brightness surface temperature for some natural surfaces. Cuenca et al.- AATSR Workshop